Traces of illegal antibiotics are lurking in America’s favorite seafood, according to a new report by ABC World News. The news outlet tested 30 imported shrimp samples from grocery stores across the country and found three were positive for antibiotics that are banned in the United States.

Though the sample size was small, the fact that 10 percent were found to contain illegal drugs is significant considering Americans annually eat 1 billion pounds of shrimp, 90 percent of which is imported from halfway across the world — mostly from Thailand, Indonesia, Ecuador, and China.

The U.S. Food and Drug Administration physically inspects less than two percent of imported seafood shipments and even smaller percentage are sampled for drug residue testing. In fiscal year 2009, for example, the FDA tested .1 percent of all imported seafood products for residues, according to the Government Accountability Office (GAO).

ABC, which has ramped up its coverage of food issues, sent the shrimp samples to the Institute of Environmental and Human Health food lab at Texas Tech University for testing. In the three positive samples, lab technicians found banned antibiotics enrofloxacin, chloramphenicol, and nitrofuranzone, which is a known carcinogen.

“About 10 percent of them showed evidence of pharmaceutical residue in the muscle tissue alone, which people eat,” Dr. Ronald Kendall, the director of the Institute told ABC. Kendall said two samples from New York averaged 28 and 29 parts per billion (ppb) of nitrofurazone. If FDA were to find 1 ppb of the drug in seafood, the product would not be allowed on the market.

It’s hard to gauge how widespread the use of antibiotics is aquaculture — and even harder to determine how often illegal drugs are used — but some experts think the industry is getting better at managing residue issues.

“I think the trend is going toward less antibiotics use,” said Jose Villalon last week at the Monterey Bay Aquarium’s Cooking for Change conference. Villalon is the vice president of the World Wildlife Fund’s U.S. Aquaculture Program, which coordinates the Aquaculture Stewardship Council (ASC). ASC is currently working on standards for the industry and aims to be the premiere certification scheme for responsible aquaculture.

For example, ASC standards do not allow any antibiotics to be used in shrimp production, but for farmed salmon, certain drugs are allowed but for very limited, targeted uses, and must be administered under veterinary supervision, according to Villalon.

“For the use that is allowed in certain species, I think the critical issue is to make sure they’re not on the World Health Organization’s list of critically important antibiotics,” he told the conference in Monterey last week. “You really don’t want to allow, even though legally they are allowed, some of those antibiotics on that list. There should be a push to eliminate it, definitely.”

Dr. Daniel Benetti, director of aquaculture at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science, who also spoke at the event in Monterey, noted that some in the industry are now turning to other compounds to combat disease.

“There’s a strong push to use probiotics nowadays…the same ones we use in yoghurt, that colonize the guts of the organisms and takes over the environment,” said Dr. Benetti. “It’s the best approach and I think that’s the direction the industry is going.”

Exactly what drugs used in aquaculture and how much of them might end up on consumers’ plates is not clear.

The GAO last year raised serious questions about the FDA’s oversight of seafood, finding that the federal program is “limited” and needs to be strengthened. The report zeroed in on the use of drugs in overseas aquaculture and the general lack of testing for both legal and illegal compounds.

Gavin Gibbons, spokesman for the National Fisheries Institute, told ABC that the trade group was “disappointed” in the test results, but didn’t think more government testing was the answer.

“Our member companies do their own sampling and testing at different times both in the exporting countries and here in the U.S.,” said Gibbons, adding that companies also invest in third party audits to help manage their supply chains.